The dye-sensitized solar cells (DSSCs) were originally developed by M. Gratzel, hence they are also called the Gratzel cells. Essentially, a DSSC is comprised of a photoanode, electrolyte, and platinum counter electrodes. The photoanode is basically a transparent and electrically conductive glass substrate formed by coating a layer of ITO or FTO film over the glass substrate, and an insulating surface formed over the conductive glass substrate includes a semiconductor film having titanium dioxide (TiO2) particles, as well as dyes adsorbed onto the semiconductor film. The Pt counter electrodes are deposited on a transparent and electrically conductive glass substrate. Electrons pass through the glass substrate on which the PT electrodes are deposited during the course of electricity generation of DSSC; accordingly the performance of DSSC will be affected by resistivity of the electrically conductive glass substrate. Further, the electrically conductive glass substrate has a relatively high share in the manufacturing costs of a DSSC.
To this date, the industry is still continuously looking for a substrate for DSCC counter electrodes having a high electric conductivity, excellent mechanical properties, a high thermal stability and a high dimension stability.
U.S. Pat. No. 7,090,793 discloses a composite bipolar plate of polymer electrolyte membrane fuel cells (PEMFC), which is prepared as follows: a) preparing a BMC material containing a vinyl ester resin and a graphite powder, the graphite powder content of BMC material ranging from 60 wt % to 80 wt %, based on the compounded mixture; b) molding the BMC material from step a) to form a bipolar plate having a desired shape at 80-200° C. and 500-4000 psi, wherein the graphite powder is of 10 mesh-80 mesh; less than 10 wt % of the particles of the graphite powder are larger than 40 mesh, and the remaining particles of the graphite powder have a size of 40-80 mesh. The disclosure of this US patent is incorporated herein by reference.
Taiwan Invention Patent No. 286579 discloses a polymer composite bipolar plate for a PEMFC, which is prepared by: a) compounding phenolic resin and carbon fillers to form a BMC material, the BMC material containing 60 to 80 wt % graphite powder, 1 to 10 wt % carbon fiber; and one or more conductive carbon fillers selected from: 5 to 30 wt % Ni-planted graphite powder, 2 to 8 wt % Ni-planted carbon fiber and 0.01 to 0.3 wt % carbon nanotubes, based on the weight of the phenolic resin, provided that the sum of the amounts of the carbon fiber and Ni-planted carbon fiber is not greater than 10 wt %; b) molding the BMC material from step a) to form a bipolar plates having a desired shape at 80-200° C. and 500-4000 psi. The carbon nanotubes used are 1) single-wall or multi-wall carbon nanotubes; 2) having a diameter of 0.7-50 nm; a length of 1-1000 μm; and 4) a specific surface area of 40-1000 m2/g. The disclosure of this Taiwan patent is incorporated herein by reference.